Turbine systems can be used to generate kinetic energy in the form of a rotating driven member. In some circumstances, the rotating driven member can be used to generate electricity, for example, by rotation of a permanent magnet within a stator. Such turbine generator systems can include a turbine wheel that rotates when the compressed gas flows toward an input side of a turbine wheel and exits to an outlet side of the turbine wheel. The compressed gas can be expanded during the flow over the turbine wheel, thereby causing the turbine wheel to rotate. As the gas expands, the temperature falls, and the gas exiting the turbine wheel is thus at a lower temperature.